Force applicator for drill bit



April 7; 1965 J. M. KELLNER ETAL 3,180,437

FORCE APPLICATOR FOR DRILL BIT 4 Sheets-Sheet 1 Filed May 22. 1961Jackson M. Keli ner LNVENTORS Thomas 0. Allen ATTORNEY April 27', 1965J. M. KELLNER ETAL 3,180,437

FORCE APPLICATOR FOR DRILL BIT Filed May 22, 1961 4 Sheets-Sheet 3 1 ause 4 as 6 [93$ IO :0 P J FIG. 8A

HG- 8B Jackson'M. Kellner INVENTORS Thomas 0. Allen QA&M

ATTORNEY April 27, 1965 J. M. KELLNER ETAL FORCE APPLICATOR FOR DRILLBIT 4 Sheets-Sheet 4 Filed May 22. 1961 IIIIII rill!- IIII! l!!! Thomas0. Allen Jackson M. Kellner INVENTORS BYM IQM FIG. HA

A T TORNE Y United States Patent 0 3,188,437 FGRQE AEPLKIATQP. FGR DRZLLBIT Jackson M. Kellner and Thomas 0. Allen, Tulsa, Okla, assignors toJersey Production Research Company, a corporation of Delaware Filed May22, 1961, Ser. No. 114,273 16 jlainis. (6!. 175-239) This inventionrelates to apparatus for applying weight to a bit that is used fordrilling wells or boreholes into the earth. More particularly it relatesto a bottom hole assembly for applying force to a drill bit therebyforcing the bit against the bottom of a borehole. This application is acontinuation-impart of co-pending application Serial No. 77,049, nowabandoned, filed December 20, 1966.

In the art of drilling wells for the production of oil and gas the mostcommonly used method is the so-called rotary drilling method. In therotary drilling method, a drill bit is suspended at the lower end of astring of drill pipe which is supported from the surface of the earth. Adrilling fluid is forced down through the drill string through the drillbit and back up to the surface through the annulus between the drillpipe and the walls of the borehole. The purpose of the drilling fluidincludes cooling the bit, carrying cuttings out of the well and also toimpose hydrostatic pressure upon high-pressure formations penetrated bythe drill bit to prevent the uncontrolled escape of oil, gas or waterduring drilling operations. Rotary drilling practice has found the rateof penetration of a drilling bit through subterranean formations isincreased by increasing the force of a drill bit against the bottom ofthe well. It has been found further that the drilling of a more nearlystraight hole is accomplished by creating a localized force in the areaimmediately adjacent the drill bit. In the latter instance, the twistingand rotative movement of lengthy strings of relatively flexible drillpipe is straightened immediately adjacent the drill bit by theapplication of such force.

The usual method that has been tried for increasing the pressure of abit on the borehole is by the addition of several heavy drill collarsbetween the drill bit and the drill string. Modern drilling practice hasindicated that a trend toward even higher bit Weight resulted in maximumdrilling rates and accordingly minimum footage cost. The use of heavydrill collars has not been completely satisfactory. While the additionof drill collars has aided the penetration rate, this advantage isofifset by the need for heavier surface equipment. Also more horsepowerand rig time are required in pulling the drill pipe, drill collars anddrill bit during normal operations of drilling such as are required whenthe drill bit becomes worn and needs replacing.

Accordingly it is the object of this invention to provide an apparatusfor use in the drilling of wells wherein a drilling fluid is utilized toapply force upon the drill bit thereby eliminating handling of longdrill collars.

Briefly, a preferred embodiment of this invention concerns upper andlower hydraulic bit loading units. An inner mandrel or arbor extendsthrough each loading unit and fluidly connects the interior of a drillstring with the bit. A lower case or section of an elongated housingsurrounds the lower part of the mandrel immediately above the drill bitand a second or upper case or section of a housing surrounds the mandreland is just above the lower case. The upper case and the lower case eachcontain thrust or pushdown means positioned between the mandrcl and thecase for exerting force on the mandrel longitudinally thereof in thedirection of the bit, and anchor means attached to each case operableupon actuation to transfer reaction thrust of the pushdown means to theborehole wall. Thus an upper and a lower bit loading units are provided.Control means are provided such that when the anchor means and pushdownmeans of one unit is being reset deeper down the hole, the other bitloading unit is operative. Differential pressure of drilling fluid whichexists across a drill bit attached to the mandrel is utilized (1) toanchor the case of the unit (being operative) to the borehole Wall, and(2) to apply force to the drill bit. A snap-acting valve arrangementoperable by movement of the inner mandrel with respect to one of thecases controls the sequences of actuation of the upper and lower bitloading units. While one bit loading unit is being reset, the other isoperative thus permitting force to be applied to the drill bit atsubstantially all times.

Other objects and a better understanding of the invention will becomemore apparent from the following description taken in conjunction withthe drawing in which:

FIG. 1A is an upper and FIG. 1B is a lower elevational view partially insection which when taken together illustrates one embodiment of thisinvention;

FIG. 2 is a sectional view taken along the line 22 of P16. 1A;

FIG. 3 is a sectional view taken along the line 33 of FIG. 13;

FIGS. 4, 5, 6 and 7 are enlarged fragmentary sectional views of thevalve mechanism representing various operational positions of the valveused in this invention;

FIGS. 8A and 8B are elevation views partially in secion which when takentogether illustrates another and preferred embodiment of the invention;

FIG. 9 is a sectional view taken along the line 9-9 of FIG. 8B;

IG. 10 is a sectional view taken along the line ill-d6 of FIG. 83;

FIG. 11A is a lower, FIG. 11B is an intermediate, and FIG. 11C is anupper elevational view, in section, which when taken together illustrateanother embodiment of this invention; and,

FIG. 12 is a sectional view taken along the line 12-42 of FIG. 118.

In the drawing in FIGS. 1A and 1B in particular, mandrel It is a hollowcylindrical member or arbor which is supported from and connected to aconventional tubular drill pipe, not shown, through drill tool joint 13.The lower end of mandrel ll) i connected to a bit 12. Thus, as shown inthe drawing, mandrel 1% provides a rigid connection between drill bit 12and the drill string. The particular advantage of such a connection willbe discussed in greater detail hereinafter. Mounted about the upperportion of mandrel 14B is upper bit loading unit 14 and about the lowerportion of mandrel 10 is a lower bit loading unit 16. The apparatus isshown suspended in borehole 18.

Upper bit loading unit includes case or housing 20 having an anchorsection 22 and a thrust or pushdown section 24. Upper case 2th issupported from mandrel lit) by lower bearing 26 and upper bearing 28.These bearings may be of the fluted rubber type. An anchor pressurechamber Ell is formed between the upper case 2%) and the exterior ofmandrel it Seals for pressure chamber are provided by sealing means 34at the lower end of the pressure chamber and seal 32 at the upper end ofthe case preferably above bearing 28. Mounting details of the variousseals and bearings illustrated in the drawing will not be shown, asmeans for mounting such seals and bearings are known. Mounted in portsin the wall of case 20 adjacentpressure chamber 3% are a plurality ofanchor shoes 36 which preferably is a metal element 38 mounted in rubber4% which seals it with the periphery of the port. Shoes 36 thus are atype which expands outwardly against the borehole wall whenpressure isapplied in pressure chamberfitl and retracts to the position shown whenpressure is released.

Below anchor section 22 is cylinder 42 defined between the outer surfaceof mandrel 10 and the inner surface of upper housing 20. Seal 34 is atthe upper end of cylinder 42 between mandrel 10 and housing 24} and seal44 is similarly at the lower end of cylinder 42. Mounted within cylinder42 ispiston 46 which can be made an integral part of mandrel it or canbe otherwise secured thereto. Mounted around the lower part of piston 46is a fluted rubber. bearing 4-3 which prevents excessive lateralmovement to piston seal ifia within cylinder 42. Mounted in the wall ofcylinder 4-2 at its lower end is plug 50 which as will be seenhereinafter is used to chargethe portion of cylinder 42 below piston 46.

Mounted about the lower portion of mandrel 10 is lower housing 52. Theupper end of lower housing 52 is reduced in diameter from the remainingportion of the housing and into a splined section 54-. Section 54 isinsertable into the lower end of upper housing 2t which is splinedinternally to match the outer splines. This'is shown clearly in FIG. 2.The splined connection between upper housing 29 and lower housing 52results in the upper housing and the lower housing being connected in. anon-rotatable but longitudinally slidable relationship with each other.

'Lower housing 52 is supported from mandrel l t} by lower bearing 56 andupper bearing 58 which maybe fiuted'rubber bearings. A seal 62 is abovefluted bearing 56 and seals the exterior of mandrel It with the interiorof lower housing '52. V

An a'nch'or'section is provided in the lower part of lower bit loadingunit 16. This includes a pressure chamber 60 defined between theexterior wall ofmandrel 1d and the interior wall of lower housing 52.Pressure chamber 6% has a lower seal 62 and an upper seal 64 which formsa seal between mandrel it and the interior part of lower housing 52.Mounted in the wall of lower housing 52 opposite pressurechamber '69 area pluralityof anchor shoes '66 which are similar to anchor shoes '36.

Mounted above the anchor section in the lower housing is a pushdown orthrust section 68 which is. similar to thrust section 24 of the upperbit loading unit; A cylinder 70 is defined between the exterior wall ofmandrel 149 and the internal wallof lower housing 52. In the lower partof cylinder 70 is charging plug 84. Cylinder 70 is of slightly greaterlength in its longitudinal dimen:

sion masts chamber Ill l. A'piston '78 is attached to'or made partofmandrel'ltl. The upper face of'piston' 78 is preferably the same size inarea'as the upper face of 1 piston de so as to have the same downwardthrust from each loading unit. The ends of the etfective'stroke ofhousing 52. When in the position shown inFIGS. 1A' and 15, upper supplyconduit 1% is in fluid communica- 82 upon which lower housing 52 canrest when in its lowermost position.

Mounted within mandrel It) is a resetting fluid conduit 86 which throughports 83 in the wall of mandrel it) below piston 78 and through port 90in mandrel ll) below piston 46 fluidly connects cylinder 4-2 belowpiston 46 with cylinder 70 below piston 78.

A lower power conduit 92 is provided within the lower part of mandrelIt). At the upper end of lower power conduit 92 is port 94 in the wallof mandrel 16. Intermediate the ends of conduit )2 is a throttle port 95in the wall of mandrel 10 which establishes fluid communication betweentheinterior of conduit 92 and the-interior of cylinder 76 above piston'78. Positioned at the lower end of power conduit 92 is inflation port98 in the wall of mandrel 1:) which establishes fluid communicationbetween the'interior of power conduit 92 and the interior of pressurechamber 6%.

An upper power supply conduit 1% for supplying power to upper bitloading unit 14 is provided in mandrel 10 and extends from-just abovelower power conduit 92 to sufficiently close together to permitconvenient operation of D-slide valve or valve ring 118 which surroundsmandrel 10.

Preferably 'in'lower housing 52 above section 63 is valve operatingchamber (shown in enlarged views in FIGS. 4, 5, 6 and 7) which is ventedat 112 to the relatively lower differential pressure existing duringdrilling conditions within'annulus 19 between the, apparatus and theborehole Wall. The valve itself operatively surrounds inner. mandrel ltland includes annular valve release cage or tube 114 which has verticalmove'n'ie'n't about man'dr'el 10 within chamber llltl. Release tube 114has a multiplicity of portsillo formed in itswall. D-type -slide valve118 is longitudinally sealed in a slidable relationship with innermandrel 10 using upper and lower shaft seals such asO-Iings 12E) andl22.Slide valve 118 is connected to valve release 'tube li l by a resilientspring means lld,

typically a resilient ela's'tomer materialbonded to the valve 138a'ndrelea'se tube' 114. Attachedto slide valve I118 are a multiplicityof spring loaded la tch fingers, 128

and llotl which are adapted to be latched or unlatched to or fromrespective upper shoulder 132 and lower shoulder- 134 a'ttached to or:made "integral with inner mandrel 149. Positive stops 13601" 133 onmandrel it] limits the vertical I dreiia; 3. p v I s Slide valve lifiisoperable toalternately connect the upper and lowersupply conduits withthe pressure-fluid. supply port 140. which is midway between shoulders132 and shoulder 1542- andextends through the wall ofv mandrel it).Whenin theposition shown inFIG. 1B, the interior of mandrel ltl isfiuidly incomrnunicaiton with lower power conduit 92 which in turn is influid communication with cylinder. 70. above piston .78 and the pressurechamber 69 of the anchor section of the lower bit loading unit.Inflation port '98 oi pressure chamber 6! is made larger thanthrottleport' o above piston '78,

In operation; this permits anchor shoes 66 to be expanded against theborehole wall. before the reaction thrust in cylinder-70 can causesubstantial upward movement of tion with annulus w through port 106 andmandrel 14?, port 116 in valve release tube 114 and vent 112. Whentravel of valve ll's with respect to manalso ls? valve 118 is in itsalternate position, it fluidly connects the interior of mandrel it withupper power supply conduit 109, which supplies power for anchor section22 and pushdown or thrust section When valve 13% is in its upperposition against stop 135, port 94 is uncovered and thus the interior oflower power conduit 2 i in fluid communication with annulus 19 throughports 116 and release tube 114 and vent 112.

The operation of the apparatus shown in FIGS. 1A and IE will now bedescribed, with attention also being directed to the views of FIGS. i,5, 6 and 7 which illustrate in greater detail the valve operatingmechanism while taken in combination with the views of FIGS. 1A and 13.

Before the device is lowered into the well bore resetting fluid, whichmay be a lightweight oil, for example, is injected through either plug84 or plug to fill cylinder it? below piston '78, the interior ofresetting fluid conduit 86 and that portion of cylinder 42 below piston46. To obtain optimum operation, the stroke of piston 78 in the lowerunit is approximately equal to the stroke of piston 46 in the upper bitloading unit. The stroke of valve release tube 314 within valveoperating chamber iii) is preferably slightly less than the stroke ofpiston '7? to prevent bumping of the pistons 73 against the shoul dersof cylinder 7% and also prevents the bumping of piston 4-5 against theshoulders of cylinder $2. A rotary drill pipe, not shown, is attachedthrough coupling 13 to inner mandrel l0 and bit 12. Drilling fluid ispumped down through the interior of the rotary drill pipe and theinterior of inner mandrel it to the bit where it passes through the bitand is circulated to the surface through the annulus E9. The pressuredrop through the bit then results in a relatively high pressure withinthe interior of mandrel 13 in a relative lower pressure in annular space1?. Assume that in the initial operation the inner mandrel and valvemechanism is in the position shown in FIGS. 1A and 1B and EEG. 4. Asmall portion of the drilling fluid passes through supply ports 14%)into the confined portion of slide valve 118 and thence through port 94into lower power conduit $2. Substantially instantaneously this pressureis transferred into pressure chamber 6% forcing anchor shoes as intoanchor contact with the borehole wall. Since throttling port 95 issmaller than inflation port $8, thrust force is delayed until the anchorshoes have been positioned. Thereafter full pressure is applied to theupper part of power piston 78 tending to force it downwardly withrespect to lower housing 52.

Rotary drilling imparted to mandrel it to bit 12 continues with slidevalve 118 traveling therewith as drilling progresse until such time asthe lower part or face 142 of valve release tube 114 engages thelowermost position of upward face 72 of valve operating chamber 113.Rotary drilling continues under the applied pressure force of lower bitloading unit 16 until the lower valve latch fingers 136 are releasedfrom latch shoulder E34 by engagement with lower release finger 2 36 asa part of release tube or cage 11 The continued downward movement ofslide valve 113 creates tension in spring means 124. (See FIG. 5.) Uponits release slide valve 113 is snapped upward, causing engagement ofupper latch fingers 123 with latch shoulder 132 as shown in FIG. 6. Inthat position, pressure supply fluid is now diverted through port 146into or through port 186 into upper power supply conduit During thedrilling operation just described in which the lower bit loading unitwas operative; that is, anchor shoes 65 were enga ed in th wall of thewell bore and pushdown piston 78 were exerting a force on the bit,resetting fluid was being forced from beneath piston 78 to port 83,resetting fluid conduit 36 and port 96 to beneath piston 46 thus drivingupper housing downwardly with respect to piston 46. During this processanchor shoe are in a relaxed position and are not enga ing the well borewall. Also during this period, the area above piston 45 and cylinder 42is not in communication with the high pressure fluid within mandrel 10but rather is in communication through the valve control means toannulus 19. It is thus seen that as piston '78 reaches the lower part ofits stroke within cylinder 759, piston 46 is driven to its uppermostposition in cylinder 42.

Due to the snap-action of valve 118 power supply is fed to upper supplyconduit 1599 nearly instantaneously with the stopping of the powersupply to the lower power supply cool 2. As the power supply is cut offto the lower bit loading unit pressure is immediately released frompressure chamber 6d and cylinder '76 thus allowing the immediateretraction of anchor shoes 66 and stopping the downward thrust of thrustsection 63. When piston 78, the lower bit loading unit 16, is at itslowermost position, piston 4-6 in the upper bit loading unit is at itsuppermost position in cylinder 42. Nearly instantaneous with slide valve113 being in its uppermost position, power is supplied through port res,upper supply conduit illa'l through valve port tea to (a) cylinder 42above piston 45 and through port Hi2 (b) to anchor pressure chamber 351Anchor section 22 is anchored securely to the borehole wall before thereis any substantial downward movement of piston 46 with respect to upperhousing This can be accomplished by making throttle port res smallerthan port and it is also effected by the throttle, in effect, of theresetting fluid beneath piston it can also be done by using resettingports and fill as throttle ports.

Drilling continues by rotating mandrel all and this time the downwardthrust is supplied by thrust section 24 of the upper bit loading unitand the reaction thrust is transferred to borehole wall by shoes 36 inthe upper part of upper housing 2% During this time the lower bitloading unit is being reset; that is, lower housing 52 is being forceddownwardly with respect to piston 78 by resetting fluid being forcedfrom beneath piston 35 downwardly through resetting supply conduit 8:5to the underside of piston 78 in the lower loading unit. During thisitme anchor shoes tit? are in a retracted position and tile lower unitmoves readily downward. Lower unit housing 52 continues to movedownwardly at twice the rate as piston 46 moves through its stroke incylinder of the upper bit loading unit. As drilling progresses and asshown in FIG. 7, contact of valve release cage lid with the upperportion of chamber ill forces release finger I127 into engagement withvalve latch fingers 12%, moving them from contact with latch shoulder3%2. Similarly, due to the potential tension created in spring means124, valve 118 is snapactingly forced dow wardly. Latch fingers 136 areengaged with latch shoulder 134 to assume the starting position as shownin FIG. 4 when the cycle above described is repeated.

Referring now to FIGS. 8A and 83, there is illustrated anotherembodiment and the best mode contemplated for carrying out the presentinvention. The apparatus shown in FIGS. 8A and 8B is similar to thatshown in FIGS. 1A and 1B, for example, it has an upper bit loading unitand a lower bit loading unit. However, the resetting of the loadingunits is different. These differences are incorporated in FIGS. 8A and8B and will now be discussed. More particularly, the resetting fluidconduit 86 and the port arrangement of the unit control sectionillustrated in FIG. 18 have been changed. A first fluid channel 15%extends from beneath piston 78 of the lower unit to above piston 46 ofthe upper loading unit. This fluid channel fluidly communicates with thelower portion of cylinder 7%) beneath piston 78 to port 152. A port 154in mandrel 1 fluidly connects fluid channel 159 with the interior ofslide valve 118 when in the position shown in FIG. 8B. When the valve isin its lowermost position the interior of fluid channel is in fluidcommunication through port 116, valve release tube 114 and through vent112 to annulus 19. The upper end of fluid channel 15 3 is in fluidanchor pressure chamber 60 in thelower loading unit to.

approximately piston 46 in the upper loading unit. Se ond fluid channel156 fluidly communicates with the under side of piston 46 into cylinder42 through port 158. Second conduit 156 fluidly connects with pressurechamber 69 of the lower anchor section through port 16h and to the upperside of piston 78 in cylinder 70 through port 162. When in the positionillustrated in FIG. 8B, second fluid conduit 156 is in fluidcommunication through port 164 to 116 and vent 112 to the annulus 19.

When slide valve 118 is in its lower position the interior of conduit156 is in fluid communication with the interior of mandrel 10 and theinterior of conduit is in fluid drill pipe and is then lowered into thebottom of a well bore. Drilling fluid under pressure is forceddownwardly through mandrel 10. When the valve mechanism is in theposition shown in FIG. 8B, fluid conduit 15% is in fluid communicationwith the high pressure fluid in mandrel 1t). Anchor section 22 isanchored to the borehole wall and downward pressure is exerted on piston46 through mandrel 10 to hit 12. The anchor shoes of section 22 areanchored securely to the borehole wall before suflicient fluid is passedthrough port 1194 above piston 46 to cause piston 46 to movesubstantially. High pressure fluid is also in fluid communication withthe under side of piston 78 of the lower bit loading unit and drives thelower outer housing 52 rapidly downwardly. When valve 118 is in theposition shown in FIG. 8B, fluidconduit 156 is in fluid communicationwith the lower pressure annulus 19. This permits the lower anchorsection to be relaxed as shown while the upper loading unit is anchoredto the borehole wall and is supplying thrust to the bit. The upperportion of cylinder it! above piston 73 of the lower unit is also influid communication with the exterior of the housing. This permits theouter housing to be pushed rapidly downwardly by the high pressure fluidentering cylinder beneath piston 78. The lower portion of cylinder 42beneath piston 46 in the upper loading unit is also fluidly connected tothe low pressure exterior of the units.

with the high pressure fluid within mandrel 1t} and fluid conduit is influid communication with the relatively low pressure annulus 19 exteriorof the units.. When in this position, the lower'anchor shoes 66 arenearly instantaneously expanded against the wall of the borehole andhigh pressure fluid enters cylinder 70 above piston 78 and beginstoexert a downward force on the mandrel. The slight throttling effect offluid through port 162 permits shoes 66 to be anchored securely beforesubstantial movement is obtained between the lower housingahd themandrel. W hen valve 118is in its lower position, the anchor section ofthe upper loading'unit is relaxed as pressure chamberfifl is in fluidcommunication with the low pressure area asis also the portion ofcylinder 42 above piston 46. However, the lower part of cylinder" 42below piston 46 is in fluid communication with the high pressure fluidin fluid conduit 156 and the high pressure fluid acts on face orshoulder of the lower parrot cylinder 42 driving upper housing 20downwardly. and resetting it where it remains reset until drill 1-2'isdrilled the length of the stroke of piston 78 at which point valve 118is snap-actinglymovedto its upper position and the cycle is repeated. Inthe apparatus shown in FIGS. 8A and 8B, the weight is applied most ofthe time to the lower unit. This is desirableas it is preferred to loadthe bit as close to the bit itself as is possible. In this embodiment,the length of the stroke of the upper unit compared to the lower unit ispreferably rather short. In fact, the stroke of piston 46 may be assmall as onefourth or less of the stroke of piston 78 of the lower unit.This is possible as the upper unit is in operation only the length oftime it takes the lower unit to be reset. This resetting time willdepend upon such factors as the length of the stroke of piston 78, theweight of the lower housing, the viscosity of the drilling fluid, thediiferehtial pressure existing across the bit, diameter and length ofthe fluid conduits, etc. However, for a unit in which the stroke ofpiston 78 is about 10 ft. and under normal drilling conditions the timefor the lower unit to reset is in the range of about 20 to 30 seconds orless. It is thus seen that in the system shown in FIGS. 8A'and 82 thatthe anchor shoes closer to the bit 12 are in operation all the timeexcept for this brief resetting period. This tends to permita'straighter hole to be drilled during the drilling operations.

Also shown in FIG. 8B is a spiraling preventer which is added about themandrel 10 just above bit 12. The spiraling preventer may be made anintegral part of mandrellfl and includes a series of spaced-apart hardsurface skates or shoes 171 spaced about the circumference of themandrel. The face 172 of each skate 171 is preferably a hard surface.spiraling preventer 17% as shown in FIG. 10 is approximately equal orslightly greater than the relaxed diameter of the anchor shoes and lessthan the gage diameter of the bit. This spiraling preventer 17% stops orreduces spiraling (bit walking) and prevents substantial reduction ofthe drift diameter of the hole. This permits more readily advancement ofthe outer case after resetting of the tool.

Turning now to FIGS. 11A, 11B and 11C there is illustrated still anotherembodiment of the invention. In this embodiment both the upper and thelower loading units are operative to exert a force on the bit at alltimes except for a brief resetting time for each bit loading unit.Controls are provided such that theunits are reset at diflerent times.Illustrated thereon is an upper loading unit 189 and lower loading unit182. Mandrel 188 is connectable at its upper end to a string of drillpipe not shown and at its lower end to a; bit 1%. Mounted about mandrel188 is upper housing 184 and lower housing 186. The upper housing andthe lower housing are interconnected in a nonrotatable, longitudi nallyslidable relationship through spline joint 192 which includes externalsplines on an upper reduced portion of the lower housing and internalsplines 1% in the bore of the lower end of upper housing 189. Thesplined connection between the upper housing and the lower housingprevents rotation of a housing as it is being reset. This featureprotects the anchor shoes as they cannot be rotated when retracted.Upper housing 186) is rotatably supported from mandrel by upper bearing198, intermediate bearing 200, and lower bearing 262, which aresupported withininte'rnal'recesses in the housing in a known mannerThese bearings can be of the fluted rubber type similarly as hearing 26.

An annular cylinder 211i is formed between the outer wall of mandrel 188and the interior of' housing 184. Upper seal 204 and intermediate seal2% disposed between housing 184 and mandrel 138 aid in making annularcylinder 21%) relatively fluid tight. Mounted in annular cylinder 210 isan annular piston 214 which is carried by or made integral withm'andrellSS. A seal 216 is provided between piston 214 and the interiorof I cylinder 21h. Piston 214 carries bearing .218 to prevent excessivelateral deformation of seal 216. Immediately. below annular cylinder 21%is pressure chamber 212 7 formed in a recessed portion of housing 184and the interior of mandrel 188. 'A'lower seal ZZilis provided just Thediameter D of the ensues? above bearing 2% between housing 184 andmandrel 188. Thus, seals 22% and 2% aid in making chamber 212 relativelyfluid ti ht. Resiliently and sealingly mounted in ports in the wall ofhousing 184 adjacent pressure chamber 212 are a plurality of anchorshoes 222 which are similar to anchor shoes 35 described above inrelation to PBS. 1A.

As shown in t e upper portion of housing 134 is valve operating chamber224 which is vented at 225 to the relatively lower pressure existingduring drilling conditions within the annulus between the apparatus andthe borehole wall. Operating in valve operating chamber 224- is aD-slide valve 228 and its component parts which are similar to the valveshown in FIG. 1B as operating within valve operating chamber lit Thevalve operatively surrounds mandrel 188 and includes annular releasecage 23% which has a plurality of ports 232,. Slide valve 228 isconnected to valve release cage 239 by resilient spring loans 23%.Attached to slide valve 228 are a plurality of spring loaded latchfingers 235 which are adapted to be latched or unlatched to or fromrespective upper shoulder 23% and lower shoulder 24%. Positive stops andon mandrel 1E3 lhnits the vertical travel of val e 228 with respect tothe mandrel.

Stops n42 and 245 on mandrel 318?: are so designed in relation to slidevalve 228 that power port 2&6 in the wall of mandrel 223 is in fluidcommunication with the interior of annular valve 223 in any position ofthe valve between upper stop 242 and lower stop 244. Mounted adjacentthe wall of the interior mandrel 133 is a power supply conduit 24%. Thisconduit is in fluid communication with pressure chamber 212 and annularcylinder 21d above piston 21 3.- through ports 2 3' and 252. Port 25%)can be slightly larger than port 252 and thus when fluid pressure isapplied, the anchor section is secured to the borehole wall prior to anysubstantial movement of housing 184 with respect to piston 214. Port 254is provided in the wall of mandrel 3.85 below port 246. When slide valve228 is in its uppermost position against stop 242 as shown in FIG. US,power supply conduit 24-3 is in fluid communication through ports 232and 2 26 with the annulus between the tool and the borehole wall.However, when valve 228 is in its lowermost position as against stop244, port 254 is in fluid communication with the interior or" the valve;thus power conduit 243 is in rluid communication with the interior or"mandrel Also shown is a resetting conduit 256 which is in fluidcommunication with the part of annulus cylinder 218 below piston 2 14.The interior of conduit 255 is also in fluid communication with port 253and in the posit on shown resetting conduit 256 is in fluidcommunication with the interior of mandrel 138. However, when slidevalve 22.8 is in its lower position against stop 244-, port 2 58 is notcovered by valve 223 and thus the part of cylinder below piston 214 isin iluid communication through conduit 25%, ports 232 and 226 with theannulus between the tool and the borehole.

Attention will now be directed toward lower loading unit 182. Lowerloading unit 382 contains a pushdown section and wall anchor sectionsimilarly as upper loading unit 139. The pushdown section includesannular cylinder 26d and piston 262 which is mounted on the mandrel E33.Below annular cylinder 26% is pressure chamber 264 in which anchor shoes265 are mounted in the wall of housing 185 similarly as shoes 222 in theupper loading unit. The lower housing 186 is rotatably andlongitudinally movable, in relation to mandrel ldfi and is supportedtherefrom by upper bearings 268, intermediate bearings 27%, and lowerbearing 27?). Associated with these hearings are upper seal 2%,intermediate seal 2%, and lower seal 278. These seals and bearings arecarried in grooves or otherwise by the housing in a known manner. Piston262 is also provided with a seal 28% and bearing 2232 similarly as seals21% and bearing 21% of piston 214.

The valve control mechanism for actuating and resetting the lower unitwill now be discussed. A valve operating chamber 284- is providedbetween the interior of the lower end of upper housing 13 and theexterior of reduced portion 2%. The valve mechanism in valve operatingchamber 284 is similar to D-slide valve 228 and its associated parts,except the slide valve 286 and its associated parts are actuated by arelative movement between upper housing 134 and lower housing 186,whereas slide valve 28 is actuated by a relative movement betweenmandrel and upper housing 184. Extending upwardly into valve operatingchamber 284- is an upper reduced portion 2% of lower housing 186 whichis decreased in size and has an internal bore approximately the size ofthe external diameter of the mandrel 188. An annular power supplyconduit 288 is provided in a recessed portion of upper reduced portionThe longitudinal length of annular conduit 28% is such that the port 2%is in communication with the power conduit 238 during the entire strokeof piston 262. Upper seal 292 above annular conduit 238 and lower seal2% below annular conduit 28% are carried by reduced portion 296 of thelower housing. Slide valve zss is resiliently supported from annularrelease cage 2% in which is provided relief port A port 3%2 is providedin the wall of upper housing 134 to vent valve operating chamber 284 tothe annulus between the apparatus and the borehole wall.

Slide valve 2% has longitudinal movement between upper step 394 andlower stop 5%. The interior of annu lar slide valve 286 is in fluidcommunication with power conduit 23% through port 388. Port 363 isarranged in relation to the annular slide valve and stops 334 and 3th:such that it is always in fluid communication with the interior ofannular slide valve ass; thus the interior of slide valve 286 is alwaysin fluid communication with the interior of mandrel 1%. In the positionshown a power fluid conduit 31% is in fluid communication with interiorof annular valve 285 through port 312 and witr annular cylinder 26%above piston 262 and with pressure chamber 254 of the anchor section ofthe lower loading unit. In the position of the valve as shown annularcylinder 25? below piston 262 is in fluid communication through reliefconduit 314 through ports 3% and 392 to the annulus.

Above stop is upper shoulder 316 and below lowe stop 3% is lowershoulder 31%. These shoulders 318 and 315 function with respect to thevalve operating mechanism similarly as stops 238 and 2d!) of the uppervalve arrangement in relation to the slide valve 228. The upper part ofvalve operating chamber 284- has a downwardly facing shoulder 32h whichis arranged to contact the upwardly facing shoulder 322 of relief cage29%. Likewise, the lower part of relief cage 2% forms a shoulder 32%which is arranged to contact the upwardly facing shoulder 326 or" thelower portion of valve operating chamber 284.

Port 312 and port 315 are arranged to contact the upwardly facingshoulder 326 of the lower portion of valve operating chamber 284.

Port 3212 and port 315 are arranged such that when slide valve 286 is inthe position shown, port 312 is in fluid communication with the interiorof the slide valve and 315 is exterior or" the slide valve. However,when the slide valve Zild is in its lower position, that is against stop3%, port 312 is above the annular slide valve and port 315 is incommunication with the interior of the slide valve. in other words, inthe position shown pressure chamber 26% of the anchor section and theupper part of cylinder 26% of the pushdown section is in fluidcommunication through conduit 330 through port 3E2 and the valve withthe interior of mandrel and the lower side of chamber 26% below piston262 is in fluid communication through conduit 3M and 315 to the exteriorof tool.

The stroke of pistons 21d and 252 are preferably about the same length.The stroke of piston 214 is preferably fing surface of annular cylinder210. The stroke, or

movement ofthe upwardhousing with respect to the lower housing necessaryto actuate valve 286 from either position, is preferably about the sameas the stroke re- "quiredto actuate valve 228. 7 Having described thestructural features of the embodiment on FIGS. 11A, 11B and 11C,attention will now be directed briefly toward its operational features.Thetool is connected-in a conventional manner to the lower end of astring of drillpipe by connecting mandrel 188 to a tool joint not shown.-The tool is lowered to the bottom of .a drill hole. Drilling fluid isthen circulated downwardly through-mandrel 188 under pressure and bit 1%is rotated by-rotating the drill pipe at the surface which in turnrotates mandrel 188. The particular relative position of upper housing184 and'lower housing 186 when operation is initiated does not matter asthe two units of the tool automatically assume their proper relationshipupon initial actuation of one or both control valve means by the upperloading unit. It will further be assumed for purpose of description'ofoperation of the tool that initially lower '-valve 286 is in theposition shown in FIG..

11B and the valve 228 isin its lowermost position against stop 244. Inthis position fluid under pressure-is anchoring both the upper loadingunit andthe lower loading unit to the borehole wall by anchor shoes 222and 266 respectively. Fluid under pressure is also urging pistons 214and 252' downwardly thus forcing the drill bit against the bottom of theborehole and the reaction thrust is being transferredto the walls of theborehole being drilled. As drilling progresses, mandrel 183 is moveddownwardly through-the upper and lower loading'units. As it movesdownwardly, it takes with it annular valve release cage 23@ similarly asdescribed above in relation to valve 118. When the mandrel reaches adownward position relative to upper housing 184, slide valve 228' issnap-actingly moved to its upperposition againststop 24-2 thus assumingthe position shown in FIG. l'lC ina-manner similarly described above inrelation to the snap-acting movement of a similar D-type-slide valve inoperating chamber 110. L

interior of mandrel 183. When-in this position, cylinder a 210 belowpiston 214 is in fluid communication through annular valve 228 withinterior of mandrel 188. The

upper loading unit housing, with its anchor section retra'c-ted, isforced downwardly. The downward'move ment of upper housing 134 causeslower shoulder 225 a of the'upper part of operating chamber 224 tostrike the upwardly facing shoulder 22 7 of release cage 230, thusforcing the slide valve to its lower position, that is against stop 24-4at which time the anchor shoes 222 engage the wall of the boreholeand'power is applied to the upper side of piston 214. It will be notedhere'that port 252 is designed such that flow is restricted suflicientlyso that the anchor section is anchored before a great deal'of forceisapplied against piston 214.

The downward movement of upper housing 134 causes shoulder 320 of-thelower valve operating chamber 284 to strike the uppershoulder 322 of thelower release cage 298. This continued downward movement of the upperhousing then causes valve 286m be snap-actingly moved downwardlysuchthat pressure chamber 2654 of the anchor sectionof the lower loadingunit 182 and cylinder 260 above piston 262 are in fluid communicationwith.

V the annulus. At the same time cylinder 2430 beneath pis ton 262 isindirect fluid communication with the interior of the mandrel 183through ports 3:15 and 308. Fluid unease? pressure thus forces the lowerhousing 1% downwardly to the end of its stroke, valve 236 issnap-actingly moved back to the position as shown in FlG.'11C. Inthis'position the anchor shoes are driven outwardly against the boreholewall and fluid pressure 'is applied against the .upper side ofpiston262, 'thus exerting a downward force on the mandrel, thus forcing thebit .190 downwardly against the bottom of the borehole.

In the operation of the apparatus shown in FIGS. 11A, 11B and 11C upperloading'lfitland the lower loading unit 182 are both in operation andexerting a downward force on the drill bit at all times'except whenbeing reset.

. However, the upper loading unit is reset at a different its lowerposition at'about thesame time that valve 2% is moved to its lowerposition. The anchor section of the upper unit is nearly instantaneouslyanchored when valve 223 gets in its lowermost positionand is anchoredapproximately as fast 'as'the' anchor sectionshoes 266 of the lower unitare retracted; Likewise, the pushdown section of the upper loading unitis actuated immediately as the anchor sectionis anchored to theborehole. Thus, for all practical purposes one of the loading units isoperative at all't irnes during the resetting'period. of the tool.Except forits resetting time, each unitis operative at all times duringd'rillingoperations. The'resetting time for each unitis rather brief,being only a matter of a few seconds. a p

' in using the tool'of this invention, drill pipe above the tool-willnormally be held in tension inorder to prevent buckling and unduewearing of the tool joints. In cases Where it is desired to apply lessforce to the 'bit than is normally furnished by the tool, the tension inthe drill string can be'increas ed by applyingupward time to the drillstring at the surface with the rig equipment to lessen theeiiectiveforce of the bit. One instance where it is frequently desirableto'do this is in reaming operations.

The ability to'control the force applied to the bit inthis manner is aparticular advantage of the tool of this iii vention.Furthen'this'reduction of force on the bit is accomplishedby'reduction-of the flow rate of the drilling fluid. A reduction'in thequantity ofthe fluid circulated reduces the fluid availablefor coolingand'lubricatlng the bit and lifting cuttingsfrom the boreholeandistherefore to be avoided. The use of a mandrel which extends through thetool and furnishes a rigid connection between the drill string and thebit as disclosed herein readily per-v mits control of the force on thebit.

While there are above described but alimited number of'cmbodiments ofthe process and system of the invention herein presented, it is possibleto produce still other embodiments without departing from the inventiveconcept herein disclosed. It is therefore desired that only suchlimitations be imposed. on the appending claims as are stated therein.

V first pushdown means positioned between said mandrel and said lowercase for exerting a force on said mandrel longitudinally thereof in thedirection of said'bit and for eXerting'the reaction thrust of such loadon said lower case; first anchor means attached to said lower case andoperable upon actuation to transfer said reaction thrust to the boreholewall; an upper case mounted around said mandrel longitudinallyabove-said lower case and in a a longitudinally slidable and rotatablerelationship'with said mandrel; second anchor means attached to saidupper case' andoperable upon actuation to engage the borehole wall;

means operable in a first condition to de-actuate said first alarms? i 3anchor means and said first pushdown means and to actuate said secondanchor means and in a second condition to actuate said first pushdownmeans and said first anchor means and (ls-actuate said second anchormeans.

2. In a rotary drilling apparatus for drilling a borehole including adrill bit and a drill string assembly and means for circulating fiuidthrough said assembly and said borehole, the improvement whichcomprises: a rigid mandrel connectable within said drill string andhaving a conduit for the flow of fluids therethrough, a first housingsurrounding said mandrel and rotatable and longitudinally movabletherewith between upper and lower positions, first thrust transfer meansinterposed between said mandrel and said first housing and actuatable tothrust said mandrel downward relative to said first housing, first wallanchor means on said first housing actuatable to lock said first housingto the wall of said borehole, a second housing surrounding said mandreland spaced longitudinally from said first housing and rotatable andlongitudinally movable between upper and lower positions on saidmandrel, second thrust transfer means interposed between said mandreland said second housing and actuatable to thrust said mandrel downwardrelative to said second housing, second wall anchor means in said secondhousing actuatable to lock said second housing to the wall of saidborehole, control means operable upon said first housing reaching saidlower position to sequentially actuate said first wall anchor means andsaid first thrust transfer means, said control means being furtheroperable upon said first housing reaching its upper position tode-actuate said first wall anchor means and said first thrust transfermeans and to actuate said second transfer means and said second wallanchor means.

3. An apparatus as defined in claim 2 in which the first and secondhousing are telescopically connected in a nonrotatable manner.

4. An apparatus for forcing a bit against the bottom of a boreholecomprising in combination: a mandrel atachable at its lower end to adrill bit, a first case mounted around said mandrel in a longitudinallyslidable and rotatable relationship therewith; first pushdown meanspositioned between said mandrel and said first case for exerting a forceon said mandrel longitudinally thereof in the direction of said bit andfor exerting the reaction thrust of such force on said first case, firstanchor means attached to said first case and operable upon actuation totransfer said reaction thrust to the borehole wall; a second casemounted longitudinally from said first case around said mandrel in alongitudinally slidable and rotatable rel tionship with said mandrel;second pushdown means positioned between said mandrel and said secondcase for exerting a force on said mandrel longitudinally thereof in thedirection of said bit and for exerting the reaction thrust of such forceon said second case; second anchor means attached to said second caseand operable upon actuation to transfer reaction thrust to the boreholewall; control means operable in a first condition to actuate said firstpushdown means and said first anchor means and to deactuate said secondanchor means and said second pushdown means and in a second condition tode-actuate said first anchor means and to actuate said second anchormeans and said second pushdown means.

5. An apparatus as defined in claim 4 with the improvement of providingpositioning means such that when said first case moves in onelongitudinal direction with respect to said mandrel the second casemoves in the opposite longitudinal direction.

6. An apparatus as defined in claim 4 in which the two cases aretelescopically connected in a non-rotatable mannor.

7. An apparatus as defined in claim 4 in which the mandrel is enlargednear its connection to the bit to a diameter substantially equal to thediameter of the first anchor means when such anchor means are in aretracted position.

8. In a rotary drilling apparatus for drilling a borehole including adrill bit and a drill string and means for circulating fluid throughsaid assembly and said borehole, the improvement which comprises: amandrel rigidly connecting said bit to said drill string and having aconduit for the flow of fluids therethrough; a first housing surroundingsaid mandrel and rotatable and longitudinally movable therewith betweenupper and lowerpositions; first thrust transfer means interposed betweensaid mandrel and said first housing and actuatable to thrust saidmandrel downwardly relative to said first housing; first wall anchormeans on said first housing actuatable to lock said first housing to thewall of said borehole; a second housing surrounding said mandrel andspaced longitudinally above said first housing and rotatably andlongitudinally movable between upper and lower positions on saidmandrel; second thrust transfer means interposed between said mandreland said second housing and actuatable to thrust said mandrel downwardlyrelative to said second housing; second wall anchor means in said secondhousing actuatable to anchor said second housing to the wall or" saidborehole; said first housing and said second housing telescopicallyconnected in a non-rotatable manner; control means being operable uponsaid first housing reaching its lower position to sequentially actuatesaid first wall anchor means and said first thrust transfer means and tode-actuate said second anchor means and said second thrust transfermeans; said control means being further operable upon said first housingreaching its upper position to de-actuate said first wall anchor meansand said first thrust transfer means and to actuate said second ransfermeans and said second Wall anchor means; housing positioning meansoperable such that when said first housing moves in one longitudinaldirection with respect to said mandrel the second housing moves in theopposite longitudinal direction with respect to said mandrel.

9. In a rotary drilling system for drilling a borehole, including adrill string and a bit, the improvement which comprises: a hollowmandrel rigidly connecting said drill string to said oh and of acharacter to convey fluid from said drill string to said bit through itsinterior, the exterior surface of said mandrel defining a lower pistonand an upper piston; a lower case surrounding said mandrel in arotatable and longitudinally slidable relationship therewith anddefining a lower cylinder for said lower piston, said lower case havingan upper and a lower position with respect to said mandrel, said lowercase further defining a valve operating chamber, such chamber being influid communication with the exterior of said lower case; a lowerpressure chamber formed between said lower case and said mandrel; anupper case above said lower case and surrounding said mandrel in arotatable and longitudinally slidable relationship therewith anddefining an upper cylinder for said upper piston; an upper pressurechamber formed between the Wall of said mandrel and said upper case;lower hydraulically expansible wall anchor means mounted in said lowercase, the interior of said lower anchor means being exposed to saidlower pressure chamber; upper hydraulically operated wall anchor meansmounted in the wall or": said upper case, the interior of said upperanchor means being exposed to said upper pressure chamber; a lowersupply conduit within said mandrel extending from near the upper end ofsaid lower case to within said lower cylinder above said lower pis tonand to within said lower pressure chamber; a first port means in thewall of said mandrel extending from the upper end of said lower supplyconduit to the exterior of said mandrel; an upper supply conduit withinsaid mandrel extending from about the upper end of said lower supplyconduit to within said upper pressure chamber and the upper cylinderabove said upper piston; a second port means in said mandrel spacedabove said first port means and fluidly connecting the interior of saidupper supply conduit with the exterior of said mandrel; a supply port insaid mandrel spaced longitudinally intermediate be- J3 tween said firstand said second ports; a sliding valve mounted in said valve operatingchamber and having an upper and a lowerpo'sition and alternatelyactuat'able between its upper and lower positions by movement of saidlower case to its upper position and its lower position respectively,said valve when in an upper position 'fluidly connects said supply portwith said second port and fluidly connects the lower port with theexterior of the lower case, said valve when in a lower position fluidlyconnects said supply port with the lower port and fluidly oonnectstheupper port with the exterior of said lower case; and a resetting fiuidconduit establishingfiuid communication between said lower cylinderbelow said lower -pist-on and said upper cylinder'below saidupperpiston.

10. An apparatus for forcing a bit against thetbottoni of the boreholecornprising in combination: a mandrel attachablcat its lowe r end to adrill bit, a first outer case mounted around'said mandrel in alongitudinally slidable and rotatable relationship therewith; firstpushdo'wn 7 means positioned between said mandrel and said first case I-means'p'ositioned between said mandrel and said second case forexerting a force on said mandrel longitudinally thereof in the directionof said bit and for exerting the reaction thrust of such force on saidsecond case; second anchor means attached to said second case andoperable upon actuation to transfer reaction thrust to the boreholeWall; and control means operable to sequentially deactuate said (a)first pushdown means and said first anchor means and (b) said secondpushdown means and said second anchor means when in a first conditionand to sequentially actuate said (a) first pushdown means and said firstanchor means and (b) said second pushdown means and said secondanchorrmeaus when in a second condition. a

11. In 'a'rotary drilling apparatus for drilling a borehole including adrill bit and a drill string assembly and means for circulating fluidthrough "said assembly and said borehole, the improvementwhichcomprises: a mandrel connectable within said drill string and includinga conduit for the flow of fluids therethrough; afirst housingsurrounding said mandrel and rotatably and longitudinallymovabletherewith between upper and lower positions; first thrusttransfer means interposed between said mandrel andsaid firsthousing;first wall anchor means carried by said first housing actuatable to locksaid first housing to the wall of said'borehole; a second housingsurrounding said mandrel rotat'ablyand longitudinally movable therewithbetween'upper and lower positions and spaced longitudinally below saidfirst housing in a non-rotatable and longitudinally movable relationshiptherewith; second thrust transfer means interposed between said mandreland said second housing and actuatable to thrust said mandrel downwardlyrelative to said second housing; second wall anchor'means carried bysaid second'housing and actuatable .to lock said secondhousing to the'wall of said borehole; first valvecontrol means operable when saidfirst housing is in its upper position with respect to said mandrel tode-actuate said first thrust transfer means andsaid first wall anchormeans and to 'driv'e said first housing downwardly with respect to saidmandrel, and in transfer means and said second wall anchor means whenthrust transfer means and said second wall anchor means upon said'secondhousing reaching its lowermost position.

12; An apparatus for forcing a bit against the bottom of a boreholecomprising in combination: a mandrel attachable ,at its lower end to adrill bit, a lower case mounted around one portionof said mandrel in alongitudinally slidable and rotatable relationship therewith, firstpushdown means positioned between said-mandrel and said lower ,c'aseforexerting a force on said mandrel longitudinally thereof in the directionof said bit and for exerting the reaction-thrust ofsuch load onrsaidlower casegfirst anchor means attached vto said lower case and operableupon actuation tetransfer saidreaction thrust tothe borehole wall; meansto prevent substantial longitudinal movement of'saidlower casewithrespectto said mandrel prior to the actuation of said first anchormeans; an upper case mounted around said mandrel longitudinally abovesaid lower case and in a longitudinally slidable and rotatablerelationship with said mandrel; second anchor means attached to saidupper case and operable upon actuation to engage the borehole wall;means operable in a first condition to de-actuate said first anchormeans and said'first pushdown means and to actuate said second anchormeans and in a-second condition to actuatesaid' first pushdown means andsaid first anchor means and de actuate said second anchor means.

13. An apparatus for forcing a bit against the bottom of a bore holecomprising in combination: a mandrel attachable at its lower end to adrill bit, a first case mounted around said mandrel in a longitudinallyslidable and rotatable relationship therewith; first pushdown meanspositioned between said mandrel and said first case for exerting aforceon said rnandrel longitudinally thereof in the direction of said bit andfor exerting the reaction thrust of such force-on said first case; firstanchor means attached to said first case and operable upon actuation totransfer said reaction thrust to the borehole wall; a second casemounted longitudinally from said first case around said" mandrel in alongitudinally slidable and rotatable relationship with said mandrel;second pushdown means positioned between said mandrel and said secondcase for exerting a force on said mandrel longitudiiially thereof in thedirection of said bit and for exerting the reaction thrust of such forceon said second case;

second anchor means attached tos'aidsecond case and 'operableuponactuation to transfer reaction thrust to the borehole wall; control mans operable in a first conchor means and said second pushdown means andin a second condition to de actuate said first anchor means and toactuate said second anchor means and said sec- 7 of a borehole whichcomprises :-a mandrel provided with means near the lower'end thereof forconnecting said mandrel to abit; an upper loading and anchoring unitmounted on said mandrel, said upper unit including means for exerting'adownward'thrust on said mandrel and means for transferring-the reactionthrust to the wall of the borehole when said upper unit is actuated;

5a lower loading and anchoring unit mounted on said i mandrel, saidlower unit including meanst for exerting a downward thrust'on. saidmandrel and means for trans- 7 -ferring the reaction thrust to-the wallof the borehole said first housing is in its lower position and to movesaid lower housing longitudinally from said first housinn andbeingfurther operable to actuatesaidsecond when said lower unit is actuated;and control means ."for alternately-actuating said upper umtand,SfilddQWeI' unit.

15. Apparatus as-defined in claim 14 wherein said upper and lowerloadingand, anchoring units are telescopically interconnected in anonfr'otatable manner.

16. Apparatus as defined in claim 14 including positioning means forapplying force to said lower loading and anchoring unit to move saidunit in one longitudinal direction with respect to said mandrel inresponse to the application of force tending to move said upper loadingand anchoring unit in the opposite direction with respect to saidmandrel.

References Cited by the Examiner UNITED STATES PATENTS 556,718 3/96Semmer 175-118 X 1,549,168 8/25 Townsend 166-187 2,223,645 12/40 Solomen175-94 2,474,453 6/49 Armitage 166-98 2,537,413 1/51 Lawrence 166-982,589,534 3/52 Buttolph 175-325 X 2,643,860 6/53 Koch 175-99 182,684,835 7/54 Moore 175-321 2,807,326 9/57 Church 166-120 2,827,2633/58 Scott et a1. 175-99 X 2,877,822 3/59 Buck 175-98 X 5 2,937,007 5/60Whittle 175-321 X 2,946,587 7/60 De Smaele 175-99 X 3,105,561 10/63Kellner 175-230 FOREIGN PATENTS 1,084,380 1/55 France.

OTHER REFERENCES Hydraulic Wall-Anchored Drill Collar Promises LowerDrilling Costs, J. M. Kellner and A. D. Roberts, vol. 58, 15 Oil and GasJournal, No. 40, Oct. 3, 1960, pp. 87-89.

CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, Examiner.

14. APPARATUS FOR FORCING A BIT AGAINST THE BOTTOM OF A BOREHOLE WHICHCOMPRISES: A MANDREL PROVIDED WITH MEANS NEAR THE LOWER END THEREOF FORCONNECTING SAID MANDREL TO A BIT; AN UPPER LOADING AND ANCHORING UNITMOUNTED ON SAID MANDREL, SAID UPPER UNIT INCLUDING MEANS FOR EXERTING ADOWNWARD THRUST ON SAID MANDREL AND MEANS FOR TRANSFERRING THE REACTIONTHRUST TO THE WALL OF THE BOREHOLE WHEN SAID UPPER UNIT IS ACTUATED;